(a) Field of the Invention
The present invention relates to an improved heat recuperator and method of recuperating heat loss from a furnace to enhance the efficiency of combustion of one or more nozzle or pre-mix burners associated with the furnace, and particularly to one or more exhaust tube recuperators each having a heat exchanger formed by an inner and outer tube concentrically secured to one another to define an annular space whereby ambient air passing through the annular chamber is heated and fed to an associated one of one or more burners for improving combustion.
(b) Description of Prior Art
Various types of heat recuperators are known such as those described, for example, in Canadian Pat. Nos. 1,154,371, issued Sept. 27, 1983, and 1,163,911, issued Mar. 20, 1984. These types of heat recuperating devices are specifically for use with radiant tubes and are constructed directly within such tubes. The disadvantage of some recuperators is that they interfere with the flame of the tube, thus affecting the efficiency of the heat source and makes it difficult, if not impossible, to adjust the flame. Further, when adapting such radiant tube assemblies to existing furnaces, it is sometimes necessary to replace all of the radiant tubes with these new assemblies or to adapt them to the existing tubes. Such adaptation is very costly and time-consuming and it is also difficult to service these recuperators as the heat exchanger is incorporated within the radiant tube. Also, because the recuperator is in direct contact with the very hot flame, within the radiant tube, the heat exchange device will deteriorate more quickly. Also, because prior art recuperators are located inside or partly inside the radiant tubes, they in effect obstruct the exhaust. If gas accumulates in the tube, prior to combustion, an explosion will take place in the tube and because these devices obstruct the tube, there will be no direct exhaust and the recuperator will be severely damaged and could cause bodily injury.